The present invention relates to land-leveling and deals more specifically with a system and method for land-leveling using the Global Positioning System (GPS).
Land-leveling is carried out for getting a desired surface and slope of the land. Proper leveling of land is crucial in agricultural farms as it ensures efficient water run-off and proper irrigation. It is also required in various other processes such as laying of railway lines and construction of buildings.
Leveling of land involves cutting as well as filling operations depending on the difference between the existing and the desired land profile. Various work implements like motor graders, dozers, compactors, pavers and profilers are available for land-leveling. A scraper is typically used for leveling in agricultural farms.
Land-leveling is traditionally carried out manually. This process consists of the following three steps: surveying, leveling and verification. The surveying process is used to construct maps of the terrain. It is carried out to identify the work areas before leveling.
The step of leveling includes the operations of cutting as well as filling: the areas that are at a higher level than the desired level are cut, while the areas that are at a lower level are filled with soil.
The verification step involves resurveying the leveled land to find the compliance of the leveled land with the desired grade map.
These three steps are performed repeatedly until the desired topography is attained. The steps of cutting and filling are based on the judgment of the operator. Hence, a large number of iterations are required to attain the desired terrain. This makes the entire process highly time consuming. Moreover, to obtain acceptable accuracy levels, highly trained personnel need to be employed.
To eliminate the abovementioned drawbacks, various systems based on ultrasound and laser have been proposed. Laser-based systems consist of a swept laser beam that forms a reference laser plane. The laser plane is so adjusted that it aligns itself with the desired terrain. The sensors attached to the blades of the scraper sense the laser plane. This information is displayed to an operator who manually adjusts the height of the implement within an acceptable tolerance range. An example of one such system is the U.S. Pat. No. 4,807,131 titled “Grading System”, assigned to Clegg Engineering Inc., Orange, Calif. This patent discloses a system that measures the elevation of the grading blade relative to the laser plane and displays parameters like target elevation, actual elevation and an allowable tolerance range to the operator. This enables the operator to adjust the position of the blades within the acceptable tolerance range.
However, laser-based systems suffer from a number of drawbacks. First, laser-based systems have a limited range because of the curvature of the Earth, light-incoherence and temperature dependencies of the equipment. The typical range of a laser-based system is less than 3000 ft, which is very small when compared to the average size of agricultural farms.
Second, laser-based systems don't provide any direct measure of accuracy and integrity of the system.
Third, laser-based systems cannot be used continuously for several reasons. As these systems don't provide the horizontal position, the operator requires visible reference markers to guide the vehicle over a field. Hence, these systems cannot be used when the visibility is low (for example at night or on a foggy day) due to the lack of markers and the blockage of the laser beam due to dust and/or fog. Due to this, an operator cannot use these systems round-the-clock.
Fourth, only two-dimensional planar profiles can be achieved using laser-based systems; it is not possible to achieve curved and/or three-dimensional profiles. Curved profiles are critical for proper irrigation in farm fields since the water follows the earth's geoidal shape rather than a flat planar surface.
The Global Positioning System is known to provide accurate and reliable position information. Various systems based on GPS are available for carrying out farming operations like seeding, cultivating, planting and harvesting. These systems use the position information of the work implement (derived from GPS data) and the information relating to the desired topography of the field to calculate the desired position of the work implement. However, none of these systems deal with land-leveling using the Global Positioning System. Some of these systems are described below.
U.S. Pat. No. 6,434,462 titled “GPS control of a tractor towed implement”, granted to Deere and Company, Moline, Ill. discloses a system that controls the tractor along with the implement connected to the tractor—a central processor controls the tractor steering actuator and the implement driving actuator.
Another such GPS-based system is disclosed in U.S. Pat. No. 5,764,511 titled “System and method for controlling slope of cut of work implement”, granted to Caterpillar Inc. This patent describes a system and method for automatically controlling the position of a work implement, which is movably connected to the vehicle. This system maintains the work implement at a pre-selected slope of cut relative to a geographic surface.
Though the abovementioned patents provide systems that control a tractor and an attached implement, they do not provide specific methods and modes of operation set forth herein for efficient and highly accurate land-leveling. From all the abovementioned systems and patents, it is apparent that there is a need for an efficient and round-the-clock land-leveling system that can achieve three-dimensional land profiles and that has a long range and can operate in different modalities depending on the requirements of the site to be leveled.